Differences in physiological traits associated with water balance among rodents, and their relationship to tolerance of habitat fragmentation

Abstract

Physiological concepts and tools can help us to understand why organisms and populations respond to habitat fragmentation in the way they do, and allow us to determine the mechanisms or individual characteristics underlying this differential sensitivity. Here, we examine food intake, relative medullary thickness and distribution/expression of water channel aquaporin-1 in three species of South American rodents that have been reported to have different levels of tolerance to habitat fragmentation (Akodon montensis, Oligoryzomys nigripes, and Euryoryzomys russatus), using a classic water deprivation experiment to assess their abilities to cope with water shortage. We believe the mechanisms underlying this differential sensitivity are related to the organisms' capacities to maintain water balance, and therefore the species more tolerant to habitat fragmentation (A. montensis and O. nigripes) should have a higher capacity to maintain water balance. We found that A. montensis and O. nigripes were more tolerant to water deprivation than E. russatus, and this difference appears to be unrelated to differences in food ingestion rate. O. nigripes showed the highest values for RMT, followed by A. montensis and E. russatus. However all species showed RMT values that were 2.2% to 14.1% below the lower prediction limit when compared to other rodents through allometric relationships. Water deprivation seems to trigger changes in the distribution of aquaporin-1, mostly for O. nigripes and E. russatus, which may contribute to water balance maintenance. Our data suggest that these intrinsic physiological differences among these species could provide a mechanism for their differential tolerance of habitat fragmentation. J. Exp. Zool. 323A: 731-744, 2015. © 2015 Wiley Periodicals, Inc.

Testis structure, duration of spermatogenesis and daily sperm production in four wild cricetid rodent species (A. cursor, A. montensis, N. lasiurus, and O. nigripes)

“…Although often captured in areas of the Atlantic Forest and savanna, there are few studies related to the reproductive biology of these wild rodent species [17][18][19][20]. It is important to mention that these biomes have been severely fragmented and degraded by human activities for hundreds of years [21][22][23][24]. As a consequence, changes have occurred in the natural habitats and species diversity [25], which can favor generalist and opportunistic species to increase their densities and dispersion, as well as increasing the number of agricultural pests and changing the natural prevalence of zoonotic pathogens in wild reservoirs [26][27][28].…”

Determinantes da sobreposição da área de vida no roedor Akodon montensis: implicações para os sistemas territoriais e de acasalamento

“…Akodon montensis is a habitat generalist species occupying a wide variety of habitats (Umetsu & Pardini 2007), persisting where forest loss is intense (Pardini et al 2010, Püttker et al 2013 and occupying biomes other than the Atlantic Forest (Paglia et al 2012). In accordance to these ecological characteristics associated with an ample niche breadth, it has been recently shown that individuals of Akodon montensis present a higher physiological plasticity in water balance compared to individuals of co-occurring rodent species that are forest specialists (Castellar et al 2015). Thus, although behavioral studies on Akodon montensis are lacking, the reported ecological and physiological plasticity is in agreement with our findings showing ample variation in individual territorial strategies, and suggests that populations of this species across its wide geographical and environmental range may present distinct territorial/mating systems.…”